1. Field of the Invention
The present invention relates to an ejector.
2. Description of Related Art
In a known ejector, fluid is drawn through a fluid suction opening by an action of an injected high speed fluid, which is injected from a nozzle of the ejector. Then, the drawn fluid and the injected fluid are mixed together in the ejector, and a velocity energy of a mixture of the drawn fluid and the injected fluid is converted into a pressure energy at a pressurizing portion (diffuser) of the ejector to increase the pressure of the mixture, so that the pressure of the mixed fluid is increased.
This kind of ejector is used in wide variety of products, such as a refrigeration cycle system or a vacuum pump, to serve as a fluid depressurizing means for depressurizing the fluid through the nozzle of the ejector or a fluid transferring means for transferring the fluid by drawing the fluid through the fluid suction opening of the ejector. Therefore, it has been demanded to mass-produce an ejector of a specified size, which can implement an appropriate performance suitable for an intended use of the product having such an ejector, at low costs and within a short period of manufacturing time.
Japanese Unexamined Patent Publication No. 2003-326196 (U.S. Pat. No. 7,165,948B2) teaches manufacturing of a nozzle of an ejector through sintering of metal powder or ceramic powder. Furthermore, Japanese Unexamined Patent Publication No. 2003-326196 (U.S. Pat. No. 7,165,948B2) and Japanese Unexamined Patent Publication No. 2006-132897 (US 2006/0119101A1) teach a tubular body of the ejector, which is formed by processing a metal tube to form corresponding large and small diameter portions by enlarging or reducing a diameter of the metal tube through plastic deformation of the metal tube. This tubular body receives the nozzle and forms a fluid suction opening and a diffuser. Furthermore, Japanese Unexamined Patent Publication No. 2007-253175 teaches manufacturing of the body through a cold forging process.
When the nozzle is formed by the sintering in the manner recited in Japanese Unexamined Patent Publication No. 2003-326196 (U.S. Pat. No. 7,165,948B2), the manufacturing costs can be reduced in comparison to a case where the nozzle is formed through a cutting process. However, the reduction of the manufacturing costs of the nozzle formed through the sintering process is smaller than the reduction of the manufacturing costs of the nozzle formed through the plastic deformation process, such as the above discussed process of forming the large and small diameter portions in the metal tube through the plastic deformation. Furthermore, in the case where the cold forging process, which is recited in Japanese Unexamined Patent Publication No. 2007-253175, is employed, although the manufacturing process can be reduced, the manufacturing time is lengthened in comparison to the above discussed process of forming the large and small diameter portions in the metal tube through the plastic deformation.
Therefore, it is desirable to use the process of forming the large and small diameter portions by the plastic deformation recited in Japanese Unexamined Patent Publication No. 2003-326196 (U.S. Pat. No. 7,165,948B2) and Japanese Unexamined Patent Publication No. 2006-132897 (US 2006/0119101A1) among the above described techniques in order to, implement the reduced manufacturing costs, the reduced manufacturing time and the mass production of the ejector.
However, in the case where the metal tube is processed through the process of forming the large and small diameter portions by the plastic deformation of the metal tube, a wall thickness of the stretched portion, which is stretched by the enlarging or reducing of the diameter of the metal tube, becomes small. Therefore, in order to achieve a predetermined strength in the manufactured nozzle or the manufactured body, the amount of enlarging or reducing the diameter of the metal tube must be appropriately limited. Therefore, the manufacturable shape of the ejector is narrowly limited in the case of the process of forming the large and small diameter portions by the plastic deformation of the metal tube discussed in the above-described documents. As a result, it may be difficult to form the ejector of desired sizes.